Background: An animal model offers the opportunity to study organs in vivo and the porcine model was chosen to simulate a renal transplantation with complications. Renal perfusion may redistribute from cortex to medulla during systemic hypovolaemia and after renal ischaemia for other reasons, but there is no consensus on this matter. We studied renal perfusion after renal ischaemia and reperfusion.
Methods: Renal perfusion distribution was examined by use of 153Gadolinium-labeled microspheres (MS) after 2 hours (hrs) and 4 hrs ischaemia of the pig kidney followed by 4 hrs of reperfusion. Intra-arterial injected MS are trapped in the glomeruli in renal cortex, which means that MS are not present in the medulla under normal physiological conditions.
Results: Visual evaluation after reperfusion demonstrated that MS redistributed from the renal cortex to the medulla in 6 out of 16 pigs (38%) subjected to 4 hrs ischaemia and in one out of 18 pigs subjected to 2 hrs ischaemia. Central renal uptake of MS covering the medullary/total renal uptake was significantly higher in kidneys subjected to 4 hrs ischaemia compared with pigs subjected to 2 hrs ischaemia (69±5% vs. 63±1%, p<0.001), and also significantly higher than in the contralateral kidney (69±5% vs. 63±2, p<0.001). Analysis of blood and urine demonstrated no presence of radioactivity.
Conclusion: The study demonstrated the presence of MS in the renal medulla in response to renal ischaemia and reperfusion suggesting that severe ischaemia and reperfusion of the pig kidney leads to opening of functional shunts bypassing glomeruli.